Use of portable computers has increased significantly over the last few years as technology has overcome many of the previous barriers of performance and affordability, and the clear advantages of mobile computing have crossed the threshold from fantasy to reality. Yet, as laptop, notebook and palmtop computers (and other manifestations of mobile computing) have become more commonplace, certain problems have arisen with regard to communication with these mobile computers.
Despite the significant increase in the use of mobile computers, it seems unlikely that desktop computers will disappear any time soon, given their inherent advantages, including greater storage, performance and display capabilities, not to mention superior connectivity and expansion flexibility.
Thus, the need for communication between mobile computers and those residing in offices and other fixed locations (as well as among mobile computers themselves) is likely to increase dramatically as remote computing becomes an accepted, if not necessary, manner of conducting business.
Yet, as a user of a single desktop computer in an office environment begins to rely on a laptop computer while traveling or at home, new problems are created, for example, by the existence of multiple versions of a file on different computers. Keeping track of which file is most current is itself a formidable task, not to mention the numerous problems inherent in maintaining two file systems, such as locating a particular file which is not stored on both systems.
Resolving these difficult problems requires, at a minimum, some method of communication (e.g., file transfer) between the two computers. Ideally, the mobile computer user desires that this communication be as seamless as possible--i.e., as if the user had taken the desktop computer on the road (complete with its high-speed link to the office network). Thus, factors such as unattended operation and automatic initiation of communications become quite important to the highly mobile computer user. Also important is the ability to execute distributed applications, which permit the remote user to take advantage of many of the benefits offered by the desktop computing environment, such as increased storage capacity and higher performance.
Moreover, it is becoming increasingly important for users of mobile computers not only to initiate communications with other computers (whether mobile or in a fixed location), but also to be on the receiving end of such communications--e.g., to receive information, such as stock quotes, on a periodic basis or to be notified that a particular file has been modified. It is therefore not surprising that new methods of communication between computers, particularly wireless communication (e.g., cellular modems), are also increasing in popularity, because such systems enable the mobile user in an unknown location to receive communications.
Yet, in the face of these trends (toward increasing use of mobile computers and emerging methods of communication among such computers) lies significant obstacles--low bandwidth, coupled with low information transfer rate. As opposed to the high-speed local area networks now inundating office environments, a relatively low-speed modem (e.g., 9600 baud) is often the fastest means of communication available to users of mobile computers. The limited amount of information which can be transferred in a given period of time is often the most significant bottleneck inhibiting the performance of useful tasks in a mobile computing environment.
Moreover, these limitations are not likely to disappear in the near future, if ever. As new methods of transferring information among computers are developed for the office environment (and among fixed locations using extremely high-speed links), the need for additional bandwidth is constantly increasing. It is thus likely that the performance and bandwidth available for remote communications with mobile computers will continue to lag behind that found in the office environment.
Yet, numerous methods of communicating with mobile computers exist today, albeit with limited utility. On one end of the spectrum lie physical file transfer methods, such as the use of floppy disks to transport files to and from a mobile computer system. Such an approach is inherently inflexible in that the user must either determine in advance which files are to be transferred or be subject to a significant period of delay while a diskette is sent by mail or some other method of transportation.
Perhaps the most common communication medium is the standard phone line, with modems on each end for converting the analog telephone signals to the digital format accepted by today's computers. Though modems are among the fastest (and highest bandwidth) methods of communicating with remote computers, they lack significant flexibility in that they are tied to a phone line and thus a fixed location--contrary to the very essence of mobile computing.
Cellular modems, on the other hand, enable the remote user in an unknown location to receive communications at unpredictable intervals, as well as to initiate communications from virtually any location. Such modems, however, currently present significant problems of reliability and extremely limited battery life, making the "continuous standby mode" (i.e., waiting for a call) impractical.
Some of these problems could be resolved by the use of pager technology (though, as discussed below, paging systems are currently used solely for the transmission of data to a person, not to a computer). Pager receivers can be left in continuous standby mode for a sufficiently long period of time to enable the remote user to recharge the batteries overnight or during some other conveniently long period of nonuse. Moreover, pager receivers, due to the use of satellite technology, are significantly more reliable than cellular modems and can receive communications from virtually any location.
Paging systems are, however, currently a one-way medium and thus cannot initiate communications. Sending a page from a computer requires a telephone call via either a standard or a cellular modem.
More significantly, however, paging systems suffer from severe bandwidth limitations. It is simply impractical to send more than a short message via existing paging systems. It is thus not surprising that paging systems have been limited to the transmission of data (e.g., a phone number or a short alphanumeric message) intended to be displayed to the remote user on an LCD or other screen in the pager receiver. Though increasing in popularity, even new applications for paging systems, including stock quotes and electronic mail, are limited to the transmission of data intended for human recipients, as opposed to commands sent to control a remote computer.
Thus, of the various available communication media, standard modems remain the primary form of communication with remote computers. Due to the limitations discussed above, typical uses involve dialing into an office computer (e.g., a network communication server) and initiating file transfers or remote operation of an office computer and/or network.
In addition to the problems noted above with respect to communication media, there is also a dearth of sophisticated communication software tailored to the needs of the mobile computer user. Even software which allows for "remote control" of another computer or network requires that the remote user initiate the communication. In order to automate the process of initiating communication with a mobile computer, one would either have to know the location of the remote computer (thus restricting the remote user's flexibility) or use a wireless link, such as a cellular modem (generally impractical in light of the limitations discussed above).
What is needed therefore is a mobile computer communication system which can be placed in a continuous standby mode without unduly restrictive battery life limitations. Such a system would allow for the manual or automated transmission of commands to the remote computer, preferably without human intervention. Because such a system would necessarily be subject to the low bandwidth limitations discussed above, the commands would likely be short in nature, though they could be sufficiently extensible to permit the subsequent use of higher bandwidth media to implement sufficiently complex commands requiring the communication of significant amounts of information.